This invention relates to a system for controlling camera-site equipment from a plurality of control sites in the field of monitoring and surveillance, and more particularly to a centralized control system for equipment at the control sites from a master controller at a control site.
FIGS. 3 and 4 are block diagrams of a system for controlling camera-site peripheral equipment in a conventional closed circuit television system (hereafter referred to CCTV). FIG. 3 shows a direct control method, while FIG. 4 shows an indirect control method. In FIGS. 3 and 4, reference numeral 31 denotes peripheral equipment at the camera site, 32 denotes a controller for controlling the camera-site equipment, 33 denotes a coaxial cable, 34 denotes a multi-conductor cable, and 35 denotes a receiver for receiving signals from the controller 32 and sending signals to the camera-site equipment.
The control system of FIG. 3 is of the direct control method, and sends signals and electric power in accordance with the control function of the controller 32 directly to the camera-site peripheral equipment through the multi-conductor cable 34. The control system of FIG. 4, which is of the indirect control system type and used where the controller 32 and the camera-site peripheral equipment are remote from each other, performs ON/OFF control of relay contacts (not shown) of the receiver 35 through the multi-conductor cable 34, and controls sending of necessary signals and electric power through the multi-conductor cable 34 to the camera-site peripheral equipment 31 in accordance with ON/OFF actions of the relay contacts of the receiver 35. Video signals from the camera are transmitted through the coaxial cable 33 to the controller 32.
In the above-mentioned systems, a multi-conductor cable is required for controlling the peripheral equipment, and in addition, when bi-directional voice information and unidirectional alarm information from the camera site are required, separate cables need to be provided for the speech communication and alarm transmission circuits. FIG. 5 is a block diagram of the conventional CCTV including speech communication and alarm transmission circuits. In FIG. 5, reference numerals 31 to 35 denote the same parts as shown in FIGS. 3 and 4. In FIG. 5, however, alarm information from the camera site is inputted into the receiver 35, and through the intermediary of the receiver 35, the alarm information is transmitted to the controller 32 by means of the multi-conductor cable 34. Reference numerals 36, 39 denote microphones, 37, 40 denote amplifiers for increasing the strength of voice input signals, and 38, 41 denote speakers. In this way, the voice signals are transmitted in two directions.
However, in the conventional systems, a video signal, bi-directional voice signal, control signal, alarm signal, and external synchronizing signal are transmitted through separate individual circuits. Therefore, in installing a control system, many cables have to be laid between the devices, making the installation work complicated and thus causing a large total installation cost. In addition, when the video signal processing unit and the camera-side control unit are in mixed form of a control system in the control site, those units cannot be operated centrally, so that control operation of them is difficult.